Auto PTT on signal (useful for digital modes like RTTY / PSK / FT8).
The 5 Transistor ESR as detailed on the EEVBlog forum.
I have created this project and made up a through hole version of the PCB as part of my Amateur Radio training / Exams.
Feel free to review / use this project. It is not my design that credit goes to Jay_Diddy_B over on the EEVBlog.
73 Paul M6KUR